Gahhhh, fortunately we don't have experience with this but I believe if a dog is doing the "boot scoot" rubbing it's butt across the floor and carpet and seems to be uncomfortable that might be the problem. You can do it yourself, but a groomer or vet might be willing instead...call your vet for advice.

The first sign is the smell. If you can smell a strong odor on your dog's behind, chances are his anal glands are full. And yes, a dog trying to lick/chew his butt or trying to scoot it on the ground is also a sign of full anal glands, especially if you see a sticky, stinky residue left behind.

If you lift the tail straight up the 6 and 8 o'clock areas below the anus will be flat or slightly depressed if the sacs are not full. If they are full you may see some swelling there. It is easier to feel if they are full than see it and individual dogs have their own point of discomfort. Sassy's sacs could not even feel firm and she would be scooting and licking while Max's sacs can be seen as actual bumps and he is fine with it. You may see some pale thick discharge at the anus too. It varies a great deal in color and consistency but looks pale against a dog's skin tones.

I have done anal glands for years and years being a groomer, but last week we had a Bassett come in and he had AT LEAST one half cup of fluid in his. I could smell them the second I picked up his tail and it looked like two tennis balls were in there. I instantly assumed infection or blocked and was ready to send him off to the vets. But, it was all relatively thin, clear liquid.
He was some happy when I was done!!!

And Sassy would be licking and scooting with a couple of drops that needed to come out.......... Even when she was leaning in and helping express it herself there would be maybe a teaspoonful of gunk trapped.

I did Toto's today, it was his grooming day, and his were chuck full but wicked, wicked thick paste. AND, there was a two to three inch long "tube" thingie that came out, too. I have no idea what it could be but it was GROSS!!! Looked like the skin off an earth worm????